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Senior Assistant-Snrgeon to the Itoyol Tr tstminster Ophthalmic Hospital ; Fellmc and late 
Vice-President of the Medical Society of London ; Member of the 
Microscopical Society, London ; etc. 


J Manual of Ophthalmoscopic Surgery, being a Treatise on the Use of the Ophthalmoscope in 
Diseases of the Eye; The Microscope, its History, Construction, and ylpplicatioiu ; 
Elements of Natural Philosophy ; etc. 





Further Observations on /Ae Vegetable^s, particularly 
those infesting the Human Skin. By Jabez Hogg, 
F.L.S., M.R.C.S., &c. 

(With Plates III & IV.) 
(Read Nov. 8, 1865.) 

Mr. President, — Since you did me the honour to ask for 
a contribution to the 'Transactions of the Microscopical 
Society' during your term of office, I thought I could not 
better engage an evening than by putting together a short 
account of some further observations I have been making, 
during the recess, on the identity of the parasitic fungi 
infesting the human skin. And I must request the members 
to receive the few remarks I am about to make as a conti- 
nuation of the investigations I communicated to the Society 
at the end of 1858, and which were published in our * Trans- 
actions,' January, 1859, wherein I endeavoured to show the 
true character of the so-called parasitic diseases of the skin, 
their common origin and identity, and also the universal 
distribution of these parasites throughout nature. 

You will, I am sure, pardon a small degree of vanity, 
when I say that it is exceedingly gratifying to me to find 
that the publication of the paper just referred to seems to 
have been the cause of directing the attention of other 
observers to this very important subject ; and by the labours 
of scientific men diseases of the skin have been gradually 
rescued from the hands of the empiric. They are now acknow- 
ledged to be consitutional rather than local afiections, and 
a simpler and more efiectual method of treatment for the 
cure of some of the greatest ills that flesh is heir to, is 
distinctly pointed out, and at once resorted to. But whether 
future investigations will tend to confirm an opinion now 
gaining ground, to the eflFect that the poison-germs which 
produce the most alarming infectious diseases are likewise 
of 2l fungoid nature, I am not at all prepared to say. But of 
this we may be quite certain, that it is only by the aid of the 
microscope, in the hands of those who will patiently sit them- 
selves down to interrogate nature, " that we can ever expect 
to make out the character of those poisons which, generated 
in one body and conveyed to another, produce such terrible 
destruction to our race."* For these microscopic germs, iu- 

* Dr. Bealc, in a highly vahiabic series of lectures " On the Passage of 
Germinal or Living Matter from one Organism to another," published in tlic 
' Medical Times and Gazette,' 1864, enters into the question of contagion. 
He believes that when germinal matter has its powers of growth perverted or 


Hogg, on Vegetable Parasites. 

visible though they be to the unaided sight, are nevertheless 
produced in myriads in the earth, air, and water around us, 
and are so diminutive that ordinary motes floating about iu 
the atmosphere are large in comparison. And when we 
reflect on the very remarkable powers of life possessed by all 
— and the fungi in particular — which are found to resist 
a moist heat equal to that of boiling water, and also an in- 
tense frost, without at all losing their powers of germi- 
nation, we can no longer feel surprised that their spores are 
found penetrating the hairs of the head or the hair-follicles 
and epidermic cells of the body ; nor, indeed, that they 
should penetrate the internal parts, even where the hard tex- 
tures, the bones, do not escape their destructive influence. 
For the very reason that these pests, botiytaceous or myco- 
dermatous fungi, are found both upon the external and in- 
ternal surfaces, it is proposed to divide them into Epiphytes 
and Entophytes. 

Although, as I have before pointed out, it is not possible 
that in either of these cases fungi originate disease, it is 
pretty certain that they frequently aggravate it, and once 
let the spores establish themselves on any part of the body 
where secretion is not sufiiciently active or healthy, and it is 
a difficult matter to throw off" the intruder. 

These, then, were exactly the conclusions I had arrived at 
seven years ago, and since this subject has engaged the atten- 
tion of oui' countrymen, it appears that men who are deservedly 
eminent on the Continent have been led to examine into the 
truth of these researches, and the result has been that Bazin, 
Hebra, and others, have considerably modified their views 
and reduced the number of species. 

It will, however, assist our investigation if I enter very 

degraded, it may obtain a power of indefinite multiplication, like the pus of 
an abscess or the secretion from purulent ophthalmia. Such pus, that is, 
such degraded germinal matter, he has shown to have the power of inde- 
pendent growth under various conditions, and to be capable of maintaining 
its vitality for long periods, if not completely deprived of moisture. When 
introduced into another animal's body, offering favorable conditions, it in- 
creases and multiplies. It would appear, then, that the growth of ill-con- 
ditioned germinal matter may be accompanied by the development of poison 
in the organism that supports it; just as the growth of mould changes the 
quality of bread, or cheese, or other substance, on and in which it is found. 
He docs not, however, assume the existence of spores or other bodies, whose 
presence he has not yet discovered, but appeals rather to the germinal 
matter whose existence and growth he has demonstrated ; and although he 
does not look for the extinction of all contagious diseases, yet he does expect 
that much good will be derived from keeping the body in an unsusceptible stale 
— by living in good and pure air, by dryness and plenty of sunlight, and es- 
pecially by general cleanliness, as preventives of these forms of disease. 

Hogg, on Vegetable Parasites. 


briefly into the early history of the parasitic diseases, and 
their recognised division into species. 

It is noAv more than a quarter of a century since Bassi, of 
Mihxn, discovered the vegetable character of a disease which 
caused great devastation among silkworms ; and, about the 
same time, Schonlein, of Berlin, was led to the detection of 
certain cryptogamic vegetable formations in connection 
with skin diseases. The observations of this distinguished 
man have been abundantly confirmed by Gruby, Remak, 
Robin, Kiichenmeister, Bennett, Jenner, and others, most 
of whom attempted to identify the fungus with the disease 
which they believed to be produced by it, and in this way 
separate and detach some of the most common skin diseases 
from the rest, and so regard them simply and almost exclu- 
sively as fungoid or parasitic diseases. Thus, the parasite 
supposed to be peculiar to, and productive of, each disease 
has been minutely described, and honoured with a name 
derived from the name of the disease which it is supposed to 
have originated, as appears in the following table : 





Porrigo favosa and 

Porrigo scutulata 

Porrigo decalvans 

Pityriasis versicolor 

Tinea favosa 

Tinea tonsurans 

Tinea decalvans 
Tinea sycosa 



Trichosis fur- 



Acliorion Sclimleinii. 

Tricophyion tonsurans. 

Microsporon, Audouini. 
Microsporon menlagra- 

Microsporon furfur. 

Now, this very tempting theory involves an important 
principle of pathology, inasmuch as it places the parasitic 
fungi above described in a category by themselves, and in- 
vests them with characteristics entirely at variance with 
those of the natiiral history of the family of fungi, whose 
leading feature appears to me to be that of selecting diseased 
and decayed structure as the soil most essential to their 
existence; Avhereas this hypothesis assigns to them healthy 
organized matter to live and prey upon, and thereby esta- 
blishing specific diseases. In examining into the truth or 
fallacy of this theory by the light of physiology, Me must 
bear in mind that the surface of the human body is supplied 
with a delicate covering, one office of which is to excrete, 
and another to eUminate or exude, cfl'etc matter from the 


Hogg, on Vegetable Parasites. 

blood. The excretion consists chiefly of epithelial scales, 
and the exudation is mostly made up of fluid and gaseous 
matters, which sometimes become condensed and dried ou 
the surface of the epidermis. The epithelial scales are 
friable and separable by very light friction during healthy 
and the transpired fluid makes its free escape, under ordi- 
nary circumstances, without any assistance from without. 
But want of cleanliness, deficient exercise, and much more 
frequently a deranged state of the health, especially a vitiated 
condition of the body, interfere with the natural processes of 
elimination ; and then the skin itself becomes diseased, and 
in this diseased condition may become infested by parasitic 
fungi, the spores and filamentous threads of which find a 
nidus in an abraded portion of the cuticle ; or, what is more 
generally the case, the shafts and roots of the hairs are 
invaded, the hairs become brittle and stunted in growth, and 
at length perish and fall ofi". 

Dr. Tilbury Fox, who in 1863 published an excellent work 
on ' Skin Diseases of Parasitic Origin,' was the fii^st to call 
the attention of the profession to a point of considerable 
practical value in conjunction with parasitic growths, namely, 
that whenever we find a fungus in connection with a skin 
disease we must look upon it as a something superadded to 
the diseased condition — " a complex condition, an eruptive 
disease plus a tinea " (P^^^^* ^7 ^^^^^ definition 

as our guide, we may^say 'withouCr^esitation that " the 
pathognomonic sign of parasitic disease of the surface is the 
infiltration and destruction of the hairs by the spores ; and 
the diagnosis can in nowise be considered perfect until 
spores or mycelia have been detected by the microscope." 
For the future, then, we must look upon parasitic disease as 
«o/z-existent without this test. I cannot, however, admit 
that this complex condition at all invalidates, as Dr. Fox 
would seem to imply, the opinion expressed by me in my former 
paper, namely, that the growth of a fungus is not necessarily 
pathognomonic of any special form of ski7i disease ; nor do I 
quite think, with him, that the complex eruptive condition is 
so entirely of a secondary character simply because in tinea 
decalvans we sometimes find the parasite in the perished and 
falling hairs unaccompanied by any eruption of the skin. In 
the course of my experience, which appears to slightly differ 
form Dr. Fox, I happen to have seen in my friend Mr. 
Hunt's practice cases of alopecia, sycosis, porrigo decalvans, 
&c.,''^ with a scaly desquamation preceding the perishing and 
falling of the hairs, and at the same time unaccompanied 

* See former paper, Vol. Vil, 'Quart. Jour. Micro. Scieuce/ 1859. 

Hogg, on Vegetable Parasites. 5 


by parasitic growth ; therefore I still believe that an 
eruptive condition of an abraded secreting surface is a very 
necessary part of the disease, and that then the skin affords 
a more particularly favorable soil for the development of the 
fungus; but leaving this part of the subject for the pi^esent, 
I shall proceed to show in an experimental and, I trust, a 
satisfactory way that the same species of fungus often 
exhibits varieties of character, as well as form, at different 
stages of development and under varied influences ; so much 
so, " that neither size nor outline affords any basis for dis- 
tinction into species until it has been ascertained, from ex- 
tensive comparison of forms brought from different localities 
in the widest area over which the species can be traced, what 
are the average characters of the type, and what their range 
of variation." (Bentham.) 

First, with regard to collecting and taking fungi, I find 
that the prevalence of damp or moist close weather is espe- 
cially favorable for the pxirpose ; while in an opposite con- 
dition of the atmosphere — fine frosty weather — I have rarely 
been able to secure a supply ; and, moreover, my experience 
has proved to me that in the winter season diseases of the 
skin accompanied by parasitic growth almost disappear from 
among the poor who frequent our skin infirmaries. Mr. 
Hunt also finds that season brings wdth it its own peculiar 
type of skin disease. 

It appears that at particular periods of the year the atmo- 
sphere is, so to speak, more fully charged with microscopical 
atoms than it is at others. The spores of the moulds 
aspergilli, penicillia, andpuccinia, are perhaps the most widely 
distributed bodies, and towards the end of the hot weather, 
or about autumn time, they are very abundant. Among those 
who have taken them at this period of the year we must ever 
associate the name of one of our body, the Rev. Lord 
Godolphin Osborne, who, I believe, first experimented in this 
way during the cholera visitation of 1858. He exposed pre- 
pared slips of glass, slightly moistened with glycerine, over 
cesspools, gully-holes, &c., near the dwellings of those where 
the disease appeared, and caught, what he named aiirozoa — 
chiefly minute germs and spores of fungi. I was favoured 
with a few specimens, one of which I have placed under a 
microscape on the table for the purpose of comparison with 
the more recent specimens taken by myself two raontlis ago ; 
a drawing made from this (see plate IV, fig. 4) exhibits spores 
almost identical with those found in the skin, &c. 

From the year 1858 to the present time I have amused 
myself by catching these floating atoms, and, so far as I can 


Hogg, on Vegetable Parasites. 

judge, tliey arc found everywhere, and in and on every con- 
ceivable thing, if we only look close enough for them. Even 
the open mouth is an excellent trap ; of this there is ample 
evidence, since we often find on the delicate membrane lining 
the mouth of the sucking, crying infant, and on the diph- 
theritic sore throat of the adult, the destructive plant 
O'idium albicans. The human or animal stomach is invaded^ 
and in a certain deranged condition we find the Sarcina 
ventriculi, with its remarkable-looking quaternate spores, its 
torulse, &c., seriously interfering with the functions of this 
organ. I may mention a curious fact in connection with 
stomach fungus, the discovery of Lehmann, namely, if an 
emulsion of casein (the casein of sweet almonds) be mixed 
with a small quantity of amygdaline and then introduced into 
the stomach of the animal, it very soon ferments, and the 
yeast-fungus quickly changes the chemical constituents of 
the mass into the poisonous substance oil of bitter almonds, 
and thus destroys the life of the animal. 

In specimens of the vomit from another fearful disease, the 
yellow fever, sent to me from Bermuda, I found a large ad- 
mixture of spores and torulse, with altered blood-corpuscles 
and disintegrated epithelial scales.* Here, then, we have 
striking examples of the ravages committed by the fungi, but 
I think no one will say we are justified in attributing either 
fever, thrush, or diphtheria, to the presence of the O'idium 
found in connection with these diseases. I might go on multi- 
plying examples of a similar kind ; but as that would incon- 
veniently extend my paper, I will rather proceed to give the 
results of experiments made with the favus fungus taken from 
the human body. 

At the time I read my former paper I was unable to show 
the result of any examination, or, indeed, make more than a 
passing allusion to favus, although a well-known form of 
disease, from the cii'cumstance of its having attracted the 
attention of Schonlein, who found a fungus growth always 

* My own observations on the presence of fungi in these vomits receive 
confirmation from Dr. Buchanan, who was sent by the Privy Council to make 
inquiries into the outbreak of yellow fever at Swansea last September. 
Upon making a microscopical examination of the vomits he discovered large 
quantities of fungus-spores, changed blood-cells, &c. Last year I met with 
fungus-spores in the chamber of the eye, a still more remarkable portion of 
the numan body, than any above alluded to. A man fifty years of age, came 
to me complaining of impairment of sight. His attention was first directed 
to the defect by the very unusual appearance of a small "plant-like body " 
always before him. By a careful examination of the eye with a magnifying 
ophthalmoscope I was quite able to satisfy myself of the presence of a small 
group of pucciiiia spores in the vitreous humour. 

Hogg, on Vegetable Parasites. 


mixed with favus crusts. The disease is one coramonly 
known as cupped ringworm, or honeycomb scall, and is now 
rarely seen in this metropolis ; therefore I consider myself 
fortunate in having been able, through the kindness of my 
friend Mr. Hunt, to investigate three cases, from each of which 
I collected scales for microscopical examination. I have 
here a few of the peculiar-looking crusts, and it will be ob- 
served that they are cupped in appearance, and of a dingy 
yellow colour. The crust is almost entirely composed of the 
Achorion, mixed with epithelial scales and broken hairs. 
"When the fungus once establishes itself, so fearful are its 
ravages that in a very short space of time the whole of the 
cutaneous surface, with the exception of the palms of the 
hands and soles of the feet, becomes covered with it. I 
attempted to obtain a photograph of one of the patients, but 
cannot say very successfully ; the print gives but a faint idea 
of the disagi'eeable picture really presented to the sight. 
Large masses of crusts fall off daily, each one leaving its 
mark behind. As the spores penetrate the hair-follicles they 
destroy the sheaths of the hairs, which shrivel up and lose 
their colouring matter, and then break off, leaving the sur- 
face bald. 

The fact of the surface becoming so entirely denuded is 
explained in this way : — The shaft of the hair is less in cir- 
cumference than the bulb, and consists of hardened, shrunken 
epithelial scales, almost devoid of germinal matter ; and the 
further removed from the bulb, the less of vital power does it 
possess, and consequently, when its nutrient supply, small 
even at first, becomes interfered with and lessened by the in- 
creasing spores, it loses the little vitality it ever had, dies, 
and drops off. In this, as in other cases, the fungus feeds 
upon the dead, and not the living, material. 

If we now take a crust and examine it more closely, it will 
be seen to be made up of an outer and older part, thick and 
dark in colour, the fungus being here in a more advanced 
stage, and chiefly composed of sporangia, spores, and mycelia, 
with fragments of several hairs imbedded in them. The 
under or inner and younger layer is paler in colour, and 
consists of spores mixed with epithelium, fatty and granular 
matters, and sometimes pus ; and I suppose we may consider 
that in some cases a very large quantity of the latter ingre- 
dient (pus) has been mixed up with the outer parts of the 
crusts. Mr. Wilson started a new theory, founded on this 
exceptional condition, namely, " that the favus matter is 
produced from the development of the nuclei of pus-cells ;" that 
the parasite is not a vegetable, or that, if it be, it might be 


Hogg, on Vegetable Parasites. 

looked upon as an example of the conversion of an animal into 
a vegetable product. It is quite possible, without a carefully 
made microscopical examination, to mistake the stroma, al- 
ways present in large quantities in favus crusts, for pus. This, 
I think, is a mistake often committed by the more casual 
observer. We will not, however, enter into any discussion 
upon this theory, nor upon one still more improbable, " the 
spontaneous generation hypothesis" — of all hypotheses the 
most gratuitous; I was almost about to say absurd. 

I must now be permitted to add a few words upon the 
physical aspect of persons suffering from favus, because, as 
I have already stated, and not without proof, that such dis- 
eases are the embodiment, or rather the im personification, of 
a weakly, unhealthy state of the body, well understood as 
the scrofulous habit; and associated with a dirty or neg- 
lected state of the skin in the majority of cases. Hebra, the 
great authority on skin diseases, lays much stress upon the 
feature of dirtiness as a cause of favus, and goes so far as to 
say that this accounts for its rarity among the upper classes 
of society. " The subject of one of the worst cases," says 
Mr. Hunt, " was a puny, half-starved boy of seventeen, whose 
appearance was that of a child of nine or ten. When he was 
taken from his miserable home into purer air, and well fed, 
the crusts died and dropped off; but when he returned to 
the wretched habitation of his parents, situated in one of the 
filthiest parts of Lambeth, and was insufficiently fed, the ve- 
getation grew again most rapidly — flourishing in the vitiated 
fluids like a vine in a mass of stei'coraceous mould." From 
this boy I obtained, in 1859, large supplies of the fungus 
crusts, and at that time, to make sure of the results of my 
examinations, I sent portions of the same to friends upon 
whose experiments I could rely for the confirmation of my 
own. Having perfectly satisfied myself, and not by one but 
by many trials, that the achorion (favus) produces as good a 
ferment, and nearly as briskly, as healthy yeast, when added 
to barley-wort, with only a slight difference of size and form, 
" a difference of degree, and not of kind," my next experi- 
ment was one slightly varied, for the piirpose of observing 
the modifying influence of light over these fermentations, 
and at the same time ascertaining if this agent at all affected 
the character of the results. I was, perhaps, led to make 
this observation from finding that yeast requires for its more 
perfect growth, not only a proper temperature, but almost 
occlusion from daylight — a fact that appears to hold good in 
the development and growth of most fungi. I therefore, in 
April last, procured a supply of fresh wort from a brewery. 

Hogg, on Vegetable Parasites. 


which I divided into three equal portions, and, for the sake of 
convenience, numbered 1, 2, and 3. Into Nos. 1 and 2 I put 
a few favus crusts; No. 1 was put carefully away in a darkened 
place, the temperature of which was about 70° Fahr.; Nos. 2 
and 3 (the latter being simply sweetwort only) I exposed to 
a good light in my sitting-room window, where the tempera- 
ture ranges from 65° to 75° Fahr.; each bottle was closely 
corked. On the second day, upon examining a portion of 
1 and 2 with a j-inch power, I found fermentation had com- 
menced, a film spreading over the M'hole surface of the liquid. 
In No. 1 were seen a fair quantity of yeast-cells, varying in 
form and size; shown in PI. Ill, fig. 1, a. No. 2 was in a 
more advanced stage, and some of the spores were rather 
larger than in No. 1. On the 4th and 5th days I took por- 
tions from all three bottles. That from No. 1 gave the best 
results J the spores, yeast-cells, were more numerous and 
spherical in form, well filled with granular matter and nu- 
merous moniliform chains of smaller spores and amorphous 
stroma, shown in fig. 1, b. Compared with a small portion 
of fresh yeast from a beer-barrel, fig. 3, the cells and spores 
appeared about half the size (in the drawing, however, these 
are represented too small). In specimen No. 2 spherical cells 
were fewer and smaller, with groups of ovoid spores mixed 
with torulse, and bacterium-like bodies, which were floating 
rapidly about ; here and there were seen tufts of penicillium, 
represented in fig. 2, a. In specimen No. 3 were numerous 
ovoid spores, without granular matter, highly refractive, and 
not unlike fat-globules. 

On the tenth day the changes seen in specimens taken from 
each bottle were still more marked. From No. 1 the spores 
were more numeroiis, but certainly rather smaller, and vari- 
able in form, and the greater portion of them were filled with 
granular or nuclear matter ; there were also groups of torulse 
mixed with still smaller spores, fig. 1, c. This specimen, 
when the cork was removed from the bottle, gave indications 
of the presence of carbonic acid, the odour was that of good 
fresh beer, and the greater portion of the heavy yeast had 
fallen to the bottom of the bottle. No. 2, on the contrary, 
had become quite of a dark colour, smelt sour, and the spores 
had much decreased in size, granular matter with bacteria 
being by far the more humerous; represented in fig. 2, b. 
The wort in No. 3 was still sweet — of a somewhat vinous 
sweetness — and the top was thickly covered over by a whitish, 
flocculent, filamentous-looking mass of mould. 

A fortnight or rather more elapsed, and then another exa- 
mination gave somewhat similar results. No. 1 was still per- 


Hogg, on Vegetable Parasites. 

fectly sweet, while No. 2 was more sour, and of a dark red 
colour ; the filamentous masses were broken up, and had fallen 
to the bottom of the fluid, and the surface was slightly covered 
with a mould. No. 3, although smelling somewhat like bad 
wine, was not much altered in colour, but on its surface 
aspergillus was growing. Six months later No. 1 was per- 
fectly sweet, exhibiting well-marked spores and torulae; 
No. 3 was rather more decomposed than it Avas on the former 
examination; and No. 3 remained the same. 

Now, upon comparing the fermentation of the achorion 
fungus with that of good healthy yeast, it will be seen to be 
almost identical. In the first place, it is as actively carried 
on by the former as by the latter. There is, however, just a 
slight difference in the size of the spores or cells already 
mentioned, those from yeast being the larger and more nearly 
spherical, Avith a greater number of reproductive spores, that 
is, cells with a single, clear, nucleated cell in their interior, 
while others are filled with a darker granular matter, and 
having only a slight tendency to coalesce or become fila- 
mentous ; while the achorion are for the most part ovoid 
and very prone to coalesce and produce elongated cells 
or torulaj. Now, with reference to the slight difference 
in size, we must look upon this as a matter of very little 
importance; for to the presence of light in the one case, 
and its almost total exclusion in the other, this difference, 
I have no doubt, is almost entirely due. It would be 
more trustworthy if comparisons of this kind could be made 
at the same stage of development ; for be it remembered that 
yeast obtained fi'om a brewery is in a more favorable state, 
inasmuch as it is stopped at a certain stage of gi'owth or de- 
velopment, and then set to begin its fermentation over again 
in fi'esh supplies of a new pabulum, which gives increased 
health and vigour to the plant ; while, on the other hand, the 
achorion, or favus fungus, is obtained and used in an ex- 
hausted state fi'om an already ill-nourished or starved-out 
soil. Neither can we attach much importance to differences 
iu size and form of the spores, for even this occm-s in yeast 
ferment ; and although the ovoid is most frequently seen in 
achorion, it is equally common to yeast when exhausted. 
This is strikingly exhibited in PI. IV, fig. 2, a di'awing made 
fi'om a drop of exhausted yeast taken from porter; here we have 
oval and elongated cells with torulje. To ensure success 
in these and similar experiments, the fungus or yeast should 
be left floating on the surface of liquids; the process is either 
cai'ried on very slowly or is entirely arrested by submersion. 

Turpin and others, iu their experiments on yeast, noticed 

Hogg, on Vegetable Parasites, 


that the cells become oval and bud out in about an hour 
after being added to the wort ; but this change depends as 
much upon temperature and density of the solution as iipon 
the quality of the yeast. It is a well-ascertained fact that 
when yeast is added to distillery wash, which is worked at a 
higher temperature than brewers^ wort, fermentation com- 
mences earlier, and the yeast-cell grows to a much larger 
size. It is, indeed, forced in this way much as a plant in a 
hothouse is, and then obtains to greater perfection in a 
shorter time. It will, howevei", be seen that it sooner be- 
comes exhausted ; and now, if we take a portion of this yeast, 
and add it to bai'ley-wort, and at the same time keep it in a 
temperature of from 60° to 65° Fahr., it ferments languidly, 
and small yeast- cells are the product. If the yeast is allowed 
to stand in a warm place for a few days it partially recovers 
its activity, but never quite. With such a yeast there is 
always a good deal of torulse mixed up with the degenerated 
cells, and sometimes a filamentous mass, which falls to the 
bottom of the vessel ; from this stage it readily passes to that 
of must and mildew, and then becomes a wasteful feeder or 

With yeast already in a state of exhaustion I have seen 
a crop of fungus produced in the head of a strumous boy, 
seven years of age, who was much out of health, and had 
suffered from eczema of the eyelids, with impetigo. The 
disease had obstinately persisted in spite of well-directed 
efforts to remove it. The scabs were frequently examined, 
but no fungus found. The mother, by the recommendation 
of a friend, washed the boy's head every morning for a week 
with stale beer. I saw the child a few days after these wash- 
ings were discontinued, and warm water only used to soak 
the scabs off. On placing portions of the broken hairs on a 
glass slip, and moistening with a drop of liquor potassse, 
spores and torulse were seen in abundance. Represented in 
PI. Ill, fig. 4. 

I have made frequent microscopical examinations since, with 
the same results. Two years have passed, and the disease 
remains uncured, although parasiticidical washings have had a 
fair trial. A change to country air and good diet always does 
more good than medicine in this case. I do not look upon 
this single experiment as at all sufficient to prove the pro- 
duction of the yeast fungus by transplantation into the human 
skin, although it is not very unlike the achorion fungus, or 
that of tinea tonsurans {tricophyton) ; but, taken with many 
negative trials that I made, to introduce both yeast and 
achorion into perfectly healthy skins, without any abrasion of 


Hogg, on Vegetable Parasites. 

surface, I think it has an important bearing on the subject of 
my paper. At all events it is a fair illustration of change of 
type,* for when Mr. Hunt saw the boy, after the disease had 
persisted for at least twelve months, he at once pronounced 
it to he pityriasis rubra or versicolor. Had the fungus played 
any part in bringing about this change in the character of 
the disease.f 

In another experiment I took portions of some j^^nicillia 
and aspergilli moulds, and upon adding these to sweet wort 
I obtained results confirmatory of Dr. Lowe's.f which were 
pretty much as follows. Having placed small quantities of 
spores in the wort, I stood them by in a warm room. On 
the second day in one of the solutions, and on the third in 
the other, fermentation had fairly set in ; the surface of the 
solution was covered with a film, which proved to be well- 
developed ovoid apores, filled with smaller granular spores 
(conidia) (fig. 5, PI. IV) . On the sixth day the cells changed 
in form and were more spherical. Again removing these to 
another supply of fresh wort, the results obtained were quite 
characteristic of exhausted yeast ferment. 

Extreme simplicity of structure characterises all moulds or 
mildews. Their reproductive organs are somewhat more 
complex, but less understood; and although at first sight 
there is some diflference in the appearances presented by their 
fruits, yet this is not sufficient to off'er a basis for classifica- 
tion. Both in penicillium and aspergillus the mycelium 

* The Rev. Mr. Berkeley, in his 'Outlines of British Fungology,' writes : 
— " It is not possible that in these cases fungi originate disease, though it is 
pretty certain that they frequently aggravate it." Nevertiieless, after this 
clearly expressed and positive statement, we find, a few pages further on, 
the following contradictory assertion : — " That a few spores rubbed into the 
sicin or inserted in it will soon jjroduce the disease known as porrigo lupinosa" 
(favosa ?). And he cites Dr. Lowe as his authority for this statemeui ; but 
on looking over this gentleman's writings, what do we Und ? Why, that in 
the course of a somewhat extended inquiry into the causes of diseases of tlie 
skin he only met with two cases in brewers' draymen, and one in a dirty 
cellarman, of parasitic growtiis, with sycosis and favus, and whicli, he tells 
us, commenced with a sore. I would ask any one conversant with these 
diseases if this at all justifies the above assertion, or proves that the parasite 
can be communicatea to, and grown upon, the healthy human skin. For my 
own part, so thoroughly satisfied am I of the utter fallacy of such a statement, 
that I should have no hesitation in submitting my own skin to be experi- 
mented upon. 

f It is only right to say that / did not follow Dr. Lowe, as some writers 
have stated, in tiiis field of inquiry. My observations on skin diseases were 
commenced at the suggestion of my friend Mr. Hunt, in 1856, and continued 
for three years before my first paper appeared in print. At that time, 1859, 
neither Mr. Hunt nor myself had heard of Dr. Lowe's researches, which, it 
appears, were communicated to a local society, and published the 
'Edinburgh Botanical Society's Transactions,' 1857. 

Hogg, 07i Vegetable Parasites. 


terminates in a club-shaped head, bearing upon it smaller 
filaments with small bead-like bodies upon the apex, piled 
one upon the other, or, more properly speaking, strung 
together ; these small bodies are termed conidia ; these, again, 
are surmounted by larger spores of a discoid shape filled with 
granular matter, and others which are quite empty. Those 
of the aspergillus are mostly without granular matter or nu- 
cleated bodies, and are more highly refractive. The pucciuia 
are club-shaped, and well filled with spores and spawn, 
while its ravages are mostly confined to our growing crops. 
It is the well-known smut or rust, the very rapid growth of 
the spores and spawn of which appear to exert a specific and 
peculiarly exhaustive action over the tissues of the plant on 
which it feeds. 

The yeast plant, in its most perfect condition, is chiefly 
made up of globular vesicles, measuring, when fully grown, 
about the ,^ ^'q ^ tli of an inch in diameter. The older cells 
are filled with granular or nucleated matter; the nucleus 
rapidly increases, and nearly fills up the parent cell, which 
then becomes ovoid, and ultimately the young cell buds out 
and is separated from the parent. Sometimes other and 
smaller cells are formed within the young one before it leaves 
the parent globule. This process goes on most rapidly until 
the supply of food becomes exhausted ; the vesicles, it would 
appear, derive their nourishment by the process of osmose, 
sucking in, as it were, certain portions of the organic fluid and 
chemically decomposing it, appropriating a part of its nitro- 
gen and throwing oflp the carbonic acid. If, however, it is 
placed in any adverse condition, it becomes surrounded by 
layers of condensed material, resulting from the death of the 
germinal matter; ultimately a mere trace of life remains, 
which, taking the form of an impalpable powder, is free to be 
driven hither and thither with every breath of air. 

From these experiments we may conclude that it matters 
little whether we take yeast, achorion, or penicillium spores, 
the resultant is the same, and depends much more on the food 
or nourishment supplied whether the pabulum contains more 
or less of a saccharine, albuminous, or nitrogenous material, 
lactic acid, &c., together with light and temperature ; whether 
we have a mould (green or blue), an achorion or yeast fungus 
produced. Diversity of form in the cells, as well as quality 
and quantity of their material contents, is certainly due to, 
and in a manner regulated and controlled by, the beautiful 
law of diffusion, which admits, separates, sifts, and refines the 
coarser from the finer, the lighter from the denser particles, 
through the porous structure of the cell- wall. 


Hogg, on Vegetable Parasites. 

In conclusion, I trust I have satisfactorily shown that — 

Ist/' There exists but one essential organism, a fungus 
whose spores find a soil common alike to the surface and the 
more secluded parts of the human or animal body.*'^^:^;:^'^^^^^^ 

2nd/ That variations in skin diseases associated with para- 
sitic growth are due to differences in the constitution of the 
person affected; to the moisture, exudation, soil, and tem- 
perature, under which the development of the fungus takes 
place. ''■'Consequently it is neither correct nor desirable to 
separate and classify them as "parasitic diseases of the skin.'' 

3rd. That parasitic gi'owths vary but little in any case,^and 
then only in degree, not in kind,''' some soils appearing to be 
better suited than others for their development, that fur- 
nished by the eruptive or secreting surface being in every 
way the most congenial ; while diversity of form, in all cases, 
arises from growth taking place either upon a sickly plant, a 
saccharine solution, or an animal tissue. 

4th. That fungi generally *excite chemical decomposition 
in the soils on which they feed,''''and it is the exclusive pro- 
vince of a certain class, when spread on the surface of an 
albuminoid, saccharine or alcoholic, or slightly acid liquid, to 
develope and grow, and during growth to give rise to either 
the alcoholic, acetic, or putrefactive fermentation. 

* What part do the fungi, or bacteria, play in the production of that 
fearful scourge of the human race, cancer? is a question not infrequently 
asked of me, since in the first edition of my book on 'The Microscope' 
(page 394, lS54i) I expressed a belief in " the fungoid origin of cancer" 
Subsequent examinations of diseased structure more or less tend to confirm 
this view ; it appears to me that in this disease we likewise have super- 
added a fungoid growth — "degraded germinal matter" — which, by its 
entrance into the circulation, produces a ferment and blood poisoning. 
The circular animal cell degenerates, and is converted into tiie ovoid or 
elongated vegetable cell ; ultimately we have the whole structure of some 
ori;an changed into that remarkable-looking caudate body, the typical cancer 
cell. This in some instances bears the most perfect resemblance to certain 
spores of fungi, and to the yeast torulse. As might be expected, its 
form is modified and its character more or less changed by the peculiar 
kind of nourishment and condensed tissue in which it is deposited and 
grows ; its powers of growth are, so to speak, perverted and degraded, and 
then, as we see in other instances, it soon obtains a power of indefinite 
multi):)lication, and destroys, not only the vitality of the organ, but the 
individual. M. Davaine believes he has traced splenic disease in slicep to 
the entrance into the blood of bacterium-like bodies, or fungi — a zymotic 
disease caused by ferment, by the rapid growth of which the life of the 
animal is quickly sacrificed to the destroyer. 


Illustrating Mr. Jabez Hogg's paper on Vegetable Parasites. 


1, a. — Second day, specimen from No. 1. Favus-ferment in barley- 

wort, set aside iu a darkened room. Yeast-cells, chiefly ovoid iu 

form, with spores and a few epithelium-scales. 
1, b. — Fifth day, specimen from No. 1. The yeast-cells more circular 

in form and larger in size. Spores and torulae, with bacterium-like 

bodies in an active state. 

1, c. — Tentli day, specimen from No. 1. Yeast-cells slightly degene- 

rating, becoming more ovoid ; torulse and bacteria. 

2, a. — Fifth day, specimen from No. 2, freely exposed to light. Small 

growth of yeast-cells, with spores and tufts of mycelia, penicilliuin, 
and a few large epithelium-scales ; bacteriuui-like bodies not drawn. 

2. h. — Tenth day, specimen from No. 2. Yeast-cells degenerating and 

disappearing; spores of mould, mycelia, and bacteria increasing. 

3. — Healthy yeast-cells fresh from a porter brewery, drawn rather 

smaller than they measured. 

4. — Portion of a scab taken from a boy suffering from eczema of eye- 

lids and impetigo of scalp, showing spores, moniiiform chains, torulse, 
mycelium, and epithelium-scales. 


1. — Fresh yeast transferred to a saccharine solution, and showing on 

the second day a tendency to degenerate. 

2. — Degenerated or exhausted yeast taken from the bottom of a porter- 

vat ; cells nearly all void, and torulee abundant. 

3. — Favus-fungus grown iu a pure saccharine solution. 

4. — Aerozoa. Spores with mycelium, &c., taken in the atmosphere during 

the cholera visitation of 1858. 

5. — Penicillium-spores. Mould growing in saccharine solution. 

6. — Aspergillus-spores growing in a saccharine solution. 

7. — Puccinia-spores growing in a saccharine solution. 

Muguilicd 400 diameters. 


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